Japan has become an aging society, resulting in an increased prevalence of coronary artery disease. However, clinical outcomes of elderly Japanese patients after percutaneous coronary intervention (PCI) remain unclear. Of the 15,227 patients in the Shinken Database, a single-hospital-based cohort of new patients, 1,214 patients who underwent PCI, was evaluated to determine the differences in clinical outcomes between the elderly (≥75 years) (n = 260) and the non-elderly (<75 years) (n = 954) patients. A major adverse cardiac event (MACE) was defined as a composite end point, including all-cause death, myocardial infarction (MI), and target lesion revascularization. Male gender and obesity were less common, and the estimated glomerular filtration rate (eGFR) was significantly lower in the elderly than in the non-elderly. Left ventricular ejection fraction (LVEF) was comparable between these groups. Left main trunk disease and multivessel disease were more common in the elderly than in the non-elderly group. Occurrence of MACE was frequent, and the incidences of all-cause death, cardiac death, and the admission rate for heart failure were significantly higher in the elderly patients. Multivariate analysis showed that prior MI, low eGFR, and poor LVEF were independent predictors for all-cause death in the elderly patients. Elderly patients had worse clinical outcomes than the non-elderly patients. Low eGFR and LVEF were independent predictors of all-cause death after PCI, suggesting that left ventricular dysfunction and renal dysfunction might synergistically contribute to the adverse clinical outcomes of the elderly patients undergoing PCI.